Physiological Reactions of Plants at CO₂ Emitting Mofettes and Thermal Effect of Emerging Gas - Probable Use for Remote Sensing

Abstract

Plants growing within mofette fields (CO2 emitting gas vents) show specific adaptations according to their extreme habitat. The closer they grow to the gas emitting vents and the higher the concentration of the escaping CO2 gas, the smaller the actual height and the total biomass of the plants. For some species a concomitant decrease in total chlorophyll was found. Additionally, photosynthesis as measured using CO2 gas-exchange and fluorescence clearly followed the same rule, being higher at the margins of the area and lower close to the vents. As fluorescence can be detected via remote sensors, chlorophyll fluorescence may be used to detect physiological changes from remote. In addition an abiotic thermal parameter may help in recognising mofettes in the field. As the flux of escaping CO2 gas from the soil may influence the soil temperature at and around the vent openings the application of infrared thermovision systems may be used additionally help to confirm their existence or detect unknown ones.The emerging gas dampens the temperature fluctuations of the soil imposed by the weather: it will cool the soil, when the gas is cooler than the undisturbed surface and it will warm the soil when the gas is warmer. Subtraction of multi-temporal IR images and setting temperature difference thresholds in difference images allows to disclose this effect and thus to detect the vents as well as their spatial extension.